It is desirable to estimate the position (or “location”) of a person in a geographic area with a reasonable degree of accuracy, and to associate that position with nearby places, things and services. Unfortunately, various techniques that estimate the position of a user are often expensive, slow or inaccurate. These shortcomings are pronounced in urban environments, where estimating the position of a person is difficult due to many challenges that must be overcome to deliver cost-effective and reliable position estimates. Even if cheaper and more reliable technologies are used, the scarcity of information regarding the locations of places, things and services, relative to the person, presents additional problems in urban environments. Accordingly, there is a need for improved techniques for estimating a position of a person, and for collecting assistance data that can be used with the position estimate to connect that person to a place, thing or service.